The summary:
Nothign in the created world can "satisfy for a sin so small as one look contrary to the will of God". That is because
God is in want of nothing, and, should all things perish, can restore them as easily as he created them
But the sin of man is far greater than a single look contrary to the will of God. Man was created to resist the temptation of the devil, but he failed to do this basic task, the very reason of his creation.
Man is therefore to honor God by overcoming the devil:
in his weakness and mortality, which he had brought upon himself, he should conquer the devil by the pain of death, while wholly avoiding sin.[...]
in man's victory the devil may be despoiled, and God recover his right.
[...]
by man God suffered loss, by man, also, He might recover His loss
From the weakness wrought by sin, he obviously cannot do so:
a sinful man can by no means do this, for a sinner cannot justify a sinner.